The processing of inter-item relations as a moderating factor of retrieval-induced forgetting

We investigated influences of item generation and emotional valence on retrieval-induced forgetting. Drawing on postulates of the three-factor theory of generation effects, generation tasks differentially affecting the processing of inter-item relations were applied. Whereas retrieval-induced forgetting of freely generated items was moderated by the emotional valence as well as retrieval-induced forgetting of read items, even though in the reverse direction (Experiment 1), fragment completion eliminated the moderation of retrieval-induced forgetting by emotional valence (Experiment 2). The results corroborate the assumption that the processing of inter-item relations is crucial for the immunization against retrieval-induced forgetting. Moreover, differential processing of inter-item relations may clarify the mixed results on moderating factors of retrieval-induced forgetting that have been reported.

the particular quality by which items are processed.
To explain how immunizations against RIF occur, two encoding processes have been proposed: distinctiveness and inter-item integration. Hunt (2006) defined distinctiveness as the processing of difference in the context of similarity. Smith and Hunt (2000) induced distinctiveness in that sense by instructing participants to state differences between to-be-learned exemplars of a semantic category.
No RIF occurred for such distinctively encoded items. The concept of distinctiveness also has already been used to explain moderations of RIF by the valence of the stimulus material. Kuhbandner et al. (2009) argue that encoding items in terms of differences between the items accounts for the immunizations of emotional material against RIF that have been reported so far. In a similar vein, Dewhurst and Parry (2000) provided evidence that memory advantages for emotional words over neutral words can be attributed to the distinctive encoding of emotional words. However, immunizations against RIF for emotional items could alternatively be explained by integrative encoding. Perhaps the usually higher semantic relatedness of emotional items compared to neutral items (Talmi & Moscovitch, 2004) makes emotional items more susceptible to integration. Integration refers to the explicit formation of connections between the items of a study list. Anderson and McCulloch (1999) manipulated integration by instructing participants either only to memorize exemplars of several categories or, while proceeding in their learning, to remember all previously presented exemplars of a category each time a new exemplar of that category was presented. The latter instruction caused an immunization against RIF.
Anderson and McCulloch also found that participants who indicated they had been engaging in spontaneous integrative rehearsal during encoding did not show RIF, whereas those participants who reported no or only little integrative rehearsal did.
Manipulating factors that affect distinctiveness and integration should influence the occurrence of RIF, depending on valence. We as- The three-factor account of generation effects assumes that generation always enhances item-specific processing, leading to a memory advantage of generated items over read items in recognition tests. Generation is also posited to enhance the processing of item-cue relations. For example, generating mumps from the cue illness produces a stronger association of the two words than reading the word pair.
Consequently, cued-recall tests reliably yield memory advantages for generated items as well. The third factor (the processing of inter-item relations) is assumed only to benefit from generation, though, when inter-item relations are congruent to item-cue relations. However, generation prevents the processing of inter-item relations when inter-item relations are incongruent to item-cue relations. Congruence exists when items have to be generated in response to the same cue.
Incongruence exists when each item of an organized list is generated in response to a different cue. For instance, the conceptual inter-item relations of exemplars of one semantic category are congruent to the name of the category but not to individual phonological rhyme cues or perceptual cues. The conceptual inter-item relations of the items mumps and influenza would be congruent to the category name illness, but incongruent to phonological cues like pumps and bonanza or perceptual cues like word fragments, for example mu…ps and in…luenza.
Item generation is a problem-solving task (cf. Jacoby, 1978). The solution consists of finding the correct response to a given cue. Therefore, the item-cue relation is of primary importance. Diverting attention to relations between items that differ qualitatively from the item-cue relation would hinder the success of generation. Hence, processing of incongruent inter-item relations is prevented. Given the task of filling in the missing letters in mu…ps and in…luenza, it would not only be unnecessary to consider the common membership of mumps and influenza in the category of illnesses, but actually would not help solving the fragments. Free recall is especially sensitive to the processing of inter-item relations. Thus, a memory advantage for generated items emerges in a free recall test if the processing of inter-item relations is enhanced because of their congruency to item-cue relations, but a disadvantage (i.e., a negative generation effect; Schmidt & Cherry, 1989) emerges in the case of incongruency.
When a generation task promotes the processing of inter-item relations because of a congruency of item-cue relations and inter-item relations, then generated items might be immunized against RIF. In the case of incongruency, however, no immunization should occur. In addition, a promotion or prevention of processing of inter-item relations by item generation should affect the moderation of RIF by stimulus qualities such as emotional valence. Assuming that differential integration or distinctiveness mediate the effects of emotional valence, a generation task promoting the processing of inter-item relations, therefore, should be able to diminish any moderation due to a general immunization against RIF, whereas a generation task preventing the processing of inter-item relations should diminish any moderation, because neither integration nor distinctiveness should arise. We thus expected RIF of emotional and neutral items to differ between a reading condition and a generation condition. Taking into account previous research on generation effects for emotional items, we assumed though that generation would similarly affect emotional and neutral baseline items (Nrp items). Berrin-Wasserman, Winnick, and Borod (2003) examined effects of item generation and emotional valence in one experiment. Generation enhanced memory for both neutral and emotional words in a similar fashion.
Drawing on postulates of the three-factor theory of generation effects, we tested the prediction that item generation would affect RIF.
We included emotional valence as an independent variable to examine the influence of generation on the moderation of RIF by this stimulus quality. Based on the assumption that the processing of inter-item relations accounts for immunization against RIF, we employed generation tasks that would either promote (Experiment 1) or prevent (Experiment 2) the processing of inter-item relations.

ExpErImEnt 1
In Experiment 1, we used the retrieval-practice paradigm, but modified the encoding phase by letting participants freely generate exemplars in response to category names as the sole cues in one experimental condition. Four negative and four neutral categories were used. In the retrieval-practice phase, half of the exemplars from two negative and two neutral categories had to be retrieved. Subsequently, recall for all items was assessed. To promote the processing of interitem relations in order to intensify a potential moderation of RIF by emotional valence, the items were presented in blocked order. In the reading condition, all exemplars of one category were presented at the same time, and in the free-generation condition, all exemplars of one category had to be generated consecutively. Assuming that influences of emotional valence were mediated by integration or distinctiveness, in the reading condition, we therefore expected less RIF of exemplars of negative categories than of neutral categories or no RIF of exemplars of negative categories at all (cf. Dehli & Brennen, 2009). In the freegeneration condition, we expected a general immunization against RIF independent of emotional valence due to the additional promotion Participants were instructed either to read lists of category exemplars, or to freely generate exemplars in response to category names. The time to read the exemplars of one category was limited to 20 s, after which a computer controlled sound signal indicated the need to turn to the next page, that is, the next category. The free-generation task was not time limited, so participants proceeded through the categories at self-determined speeds, turning to the next page after having written down six exemplars. In the reading condition, each page had a category name printed at the top and six exemplars underneath it. In the free generation condition, only a category name was printed at the top of the page. The first and the last category were the two filler categories.
The experimental categories were presented as alternating negative and neutral categories. In both conditions participants were instructed to memorize the exemplars for a later test.
After the encoding phase, participants performed a first distractor task: 5 min of algebra. In the subsequent retrieval-practice phase, participants were given another stack of sheets. On the first page they were instructed that the next pages contained category names together with word stems of previously studied exemplars, and that they should recall the demanded items and complete the word stems. The next page contained the three-letter word stems of four items from the filler categories, each additionally cued with the corresponding category name (e.g., cereal-bar…). The subsequent pages then each contained word stems of items of the four to-be-retrieved-practiced categories (e.g., illness-inf…). The order of presentation was randomized. After all the word stems of the Rp+ items had been presented, they were presented again in the same fashion, but in a different random order. So, every Rp+ item had to be retrieved twice. The repeated retrieval of the Rp+ items is a usual procedure intended to ensure the occurrence of RIF.
Then four word stems of four items from the filler categories were presented. The participants proceeded through this task at individually determined speeds. In the reading condition, we counterbalanced which categories were practiced and, also, which exemplars within a category were practiced. This process yielded four retrieval-practice sets. In the free-generation condition, the experimenter compiled the individual sets for the subsequent retrieval-practice during the preceding distractor task. He selected half of the exemplars from half of the categories the participant had generated, typed the three initial letters of the selected exemplars into a personal computer in order to create the retrieval-practice set, and finally printed the set. We counterbalanced which categories were practiced. In addition, for half of the participants, the items generated at the first, fourth, and sixth position were selected, for the other half, the items generated at the second, third, and fifth position were selected. After a second distractor task -3 min of algebra -the test phase began. Participants were given a third stack of sheets. On the first page they were instructed that every subsequent page contained a category name and that they should write down all exemplars they could recall from the encoding phase in 30 s. The next page contained the name of the filler category planet. Then the names of the experimental categories were presented in a random order. It is known that the first items that are produced in a recall task can interfere with the retrieval of related items (Roediger & Schmidt, 1980). Lower recall of Rp-Items compared to Nrp items might reflect such output interference instead of RIF. Perhaps, participants initially retrieved the highly accessible Rp+ items. This might have interfered with the retrieval of the less accessible Rp-items. The difference in recall performance between Rp-items and Nrp items should be the larger, the earlier Rp+ items were retrieved. To investigate potential contributions of output interference, a difference score was calculated for each participant by subtracting the average recall position of Rp+ items from the average recall position of Rp-items (cf. Macrae & MacLeod, 1999). Then, a median split on these scores constituted an early Rp+ group and a late Rp+ group in each encoding condition, and their respective forgetting effects were compared, calculated as the difference in recall performance for Nrp items and Rp-items. With regard to the previously reported reliable forgetting effects, the early Rp+ groups did not produce larger forgetting effects than the late Rp+ groups, but, in fact, the forgetting effects were slightly smaller (read exemplars of neutral categories: .13 vs. .14; freely generated exemplars of negative categories: .08 vs. .12).

Results and discussion
In summary, free generation did not immunize against RIF. It is possible that the generation task did not promote the processing of inter-item relations -or at least not as strongly as expected. However, the processing of inter-item relations probably was not prevented by generation either. Presumably, the different item material in the two conditions exerted stronger influences than differences in the processing of inter-item relations.
A partial immunization against RIF emerged in both encoding conditions, even though in opposing directions. The idiosyncrasy of the generated items may account for an opposing susceptibility to inter-item integration or distinctiveness, depending on the emotional valence. In a way, the generated items might have resembled the autobiographical memories used as the item material in the studies of Wessel and Hauer (2006) and of Harris et al. (2010) in which no forgetting for positive, but only for negative autobiographical memories occurred. Autobiographical memories and the more abstract material of exemplars of semantic categories in our study both have to be generated individually and differ from participant to participant. Such freely generated items are perhaps generally highly self-relevant, whereas preselected items are not, and negative self-relevant information may be more prone to forgetting than neutral and positive information.
If this is true, using a generation task that requires the generation of exactly the same items as in the reading condition should disentangle the influences of generation and the influences of differential item material.

Results and discussion encoding Phase and retrieval-Practice Phase
The participants correctly completed 99.2% of the fragments. The remaining (not or incorrectly completed) items were excluded from all further analyses. Retrieval success in the retrieval-practice phase was 98.1%.

test Phase
Recall rates in the test phase are shown in Table 2 The investigation of potential contributions of output interference showed that the early Rp+ group again did not produce larger forgetting effects than the late Rp+ group (neutral categories: .08 vs. .10; negative categories: .10 vs. .12).
We also compared the recall performance for Nrp items with the recall performance for Nrp items in the reading condition of Experiment 1. Significantly fewer Nrp items were recalled in Experiment 2, t(78) = 2.34, p < .05 (two-tailed). This negative generation effect indicates that the processing of inter-item relations, in fact, was prevented.
In summary, no immunization against RIF emerged. Fragment completion apparently prevented the processing of inter-item relations. Accordingly, exemplars of negative categories just as exemplars of neutral categories could not be integrated, neither could they be processed distinctively.

GEnEral dIscussIon
RIF of generated items differed from RIF of read items. The aim of our investigation was to test predictions derived from the three-factor theory of generation effects (McDaniel, Waddill, & Einstein, 1988;Steffens & Erdfelder, 1998). On the one hand, based on the assumption that the processing of inter-item relations accounted for immunization against RIF, we expected to find a general immunization for items generated in a task promoting the processing of inter-item relations or the emergence of RIF only for negative but not for neutral items. The  Wessel & Hauer, 2006). The self-relevance of freely generated material in general might determine that negative material is forgotten easily, but neutral and positive material is not. On the other hand, no immunization for items generated in a task preventing the processing of inter-item relations was expected.
Freely generated items were not generally immunized against RIF.
The emotional valence moderated forgetting for freely generated and for read items (Experiment 1), but not for items initially completed from word fragments (Experiment 2).
The immunization against RIF of read exemplars of negative categories corresponds with previous investigations (e.g., Dehli & Brennen, 2009). The results for freely generated items, on the other hand, resemble the results obtained by Wessel and Hauer (2006) and by Harris et al. forgetting, but not negative information. The function of such a partial immunization against forgetting might lie in the higher self-relevance of neutral and positive information (cf. Macrae & Roseveare, 2002). In the task of free generation used here, participants spontaneously named the first instances that popped into consciousness. Perhaps a high degree of self-relevance characterized these associations. Negative information then might be forgotten more easily as opposed to neutral information, due to some self-serving purpose. Analogically, the research on self-reference effects in memory has consistently shown that in normal subjects self-referentially processed neutral or positive information is better retained than negative information (e.g., Kuiper & Derry, 1982).
We consider the prevention from processing of inter-item relations in Experiment 2 as accounting for the absence of a difference in forgetting for items of negative and neutral categories there. Of course, this assumption needs further empirical support. Future studies might seek to identify other properties that are associated with differential forgetting and then to investigate if those differences do not occur following an initial task that prevents the processing of inter-item relations, just as fragment completion did here. Besides, the mixed results concerning the role of emotional valence for RIF perhaps can be seen not only to be due to differences in emotional intensity (Kuhbandner et al., 2009), but also to the congruency, or respectively, incongruency of It was not within the scope of our study to differentiate between distinctiveness and integration as accounting for immunizations against RIF. Instead, the processing of inter-item relations, arguably being the common basis of both processing qualities, was manipulated. With regard to integration, the importance of inter-item relations should be apparent. The better the processing of inter-item relations, the better can items be integratively connected. If, however, distinctive encoding caused the partial immunizations against RIF, the results demonstrated a dependence of distinctiveness on inter-item relations that seldom has been taken into consideration in the investigation of distinctiveness.
Indeed, distinctiveness is often equated with item-specific processing.
Hunt (2006), in contrast, elucidates the importance of defining distinctiveness as the processing of difference in the context of similarity by highlighting the necessity of operating with precise concepts when researching memory and of relinquishing redundant terms in order to avoid imprecise theoretical models and circularity. Our investigation concurs with this notion. The three-factor account of generation effects represents a model that provides sophisticated assumptions about the co-action of three different encoding processes. In the present context, the three-factor account possibly needs to be even further elaborated by differentiating the third factor, the processing of inter-item relations, into integrative versus distinctive encoding. In any case, the application of this model to the phenomenon of RIF and its moderation by emotional valence showed that the third factor is of crucial importance regarding the answering of the question as to how retrieval affects generated as opposed to read information.